Yoyo with propeller blades

ABSTRACT

In an example embodiment, a yoyo includes an axle, a first body and a second body coupled to the axle, and a string windable about the axle within a gap between the first body and the second body. The first body may include an outer rim and multiple propeller blades that extend inward from the outer rim toward the axle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. Provisional Application No. 62/097,074, filed Dec. 28, 2014, which is incorporated herein by reference.

FIELD

Example embodiments described herein relate to a yoyo with propeller blades.

BACKGROUND

Unless otherwise indicated, the materials described in the background section are not prior art to the claims in the present application and are not admitted to be prior art by inclusion in this section.

The yoyo is a toy which originated with the ancient Greek and is more than 2400 years in use. In its simplest form, the yoyo consists of an axle connected to two disks, and a length of string looped around the axle, similar to a slender spool. It is played by holding the free end of the string known as the handle (usually by inserting one finger in a slip knot) allowing gravity or the force of a throw to spin the yo-yo and unwind the string, then allowing the yo-yo to wind itself back to one's hand, exploiting its spin and the associated rotational energy.

Many inventions exist which minimize the friction between the axle and the string. Lower friction results in the ability for the yoyo to spin freely while the string is completely unwound. Softly touching the yoyo to the ground while it is thus spinning creates a forward or reverse motion for the yoyo and is a common trick with the yoyo.

The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.

BRIEF SUMMARY OF SOME EXAMPLE EMBODIMENTS

Example embodiments described herein relate to a yoyo with propeller blades.

In an example embodiment, a yoyo includes an axle, a first body and a second body coupled to the axle, and a string windable about the axle within a gap between the first body and the second body. The first body may include an outer rim and multiple propeller blades that extend inward from the outer rim toward the axle.

In another example embodiment, a yoyo includes a first body rotatable about an axis of rotation, a second body coupled to the first body and rotatable about the axis of rotation, and a string seat. The second body may be directly coupled to the first body, or indirectly coupled to the first body through an intervening component, such as an axle. The first body includes a first outer rim and multiple first propeller blades that extend radially inward from the first outer rim. The second body includes a second outer rim and multiple second propeller blades that extend radially inward from the second outer rim. The string seat axially separates the first body from the second body. A string is windable and unwindable about the string seat to cause rotation of the yoyo about the axis of rotation.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 illustrates an example operating environment;

FIGS. 2A and 2B include a perspective view and an exploded perspective of an example yoyo;

FIG. 3 includes a perspective view of another example yoyo; and

FIGS. 4A-4D include side views of more example yoyos, all arranged in accordance with at least one embodiment described herein.

DETAILED DESCRIPTION OF SOME EXAMPLE EMBODIMENTS

Reference will now be made to the drawings to describe various aspects of some example embodiments of the invention. The drawings are diagrammatic and schematic representations of such example embodiments, and are not limiting of the present invention, nor are they necessarily drawn to scale.

FIG. 1 illustrates an example operating environment 100, arranged in accordance with at least one embodiment described herein. In the operating environment 100, a user 102 plays a yoyo 104 using a string 106 of the yoyo 104. The yoyo 104 includes first and second bodies 108 and 110 that rotate about an axis of rotation 112. One or both of the first and second bodies 108 and 110 may include propeller blades that impart a thrust 114 on the yoyo 104 in a direction that is parallel to the axis of rotation 112. As used herein, terms such as “first,” “second,” and other ordinal terms may be used to distinguish between multiple otherwise similarly-named components without denoting an order or preference unless context dictates otherwise.

As illustrated in FIG. 1, when the yoyo 104 is thrown in a generally horizontal direction with the axis of rotation 112 generally arranged vertically, the thrust 114 may generally be directed in a vertical upward direction to counteract, or at least partially counteract, the effects of gravity. As a result, the yoyo 104 may return to the user 102 generally horizontally without dropping, or without dropping as much as yoyos that lack propeller blades.

The thrust 114 imparted by rotation of the propeller blades may allow the string 106 of the yoyo 104 to be longer than strings used in other yoyos. In particular, other yoyos that lack propeller blades may lack thrust to counteract the effects of gravity. As such, other yoyos may be limited to use with strings that are generally shorter than a maximum distance between ground (or any other surface on which a user is standing) and the user's hand that is holding a handle of the string. Strings in these other yoyos may be around four feet or less to avoid a situation where the user throws or drops the yoyo and the yoyo hits ground before reaching an end of the string.

In comparison, the string 106 may have a length greater than a maximum distance between ground and the hand of the user 102. For instance, the string 106 may have a length greater than four feet, such as a length of four feet or more, ten feet, twenty feet, thirty feet, or even forty feet or longer. Without the thrust 114 imparted by rotation of the propeller blades, the yoyo 104 may fall to ground before returning to the user 102 with such a long string 106. However, the thrust 114 imparted by the propeller blades counteracts or at least partially counteracts the effects of gravity so that the yoyo 104 may return to the user 102 without hitting ground even when the string 106 is relatively long.

As illustrated in FIG. 1, a first end of the string 106 may be attached to or held by the user 102 while an opposite second end of the string 106 may be attached to the yoyo 104. In some other embodiments, the first end of the string may be attached to an object which the user 102 may hold without the first end of the string 106 necessarily being attached to or held directly by the user 102.

The second end of the string 106 has been described as being attached to the yoyo 104. Play with the yoyo 104 when the string 106 is attached to the yoyo 104 may be referred to as on-string play. In on-string play, the second end of the string 106 is always attached to the yoyo 104, e.g., to a corresponding string seat (described below) of the yoyo 104, which allows the string 106 to be wound and unwound about the string seat without the yoyo 104 being completely free of the string.

In other embodiments, the second end of the string 106 may not be attached to the yoyo 104. Play with the yoyo 104 when the string 106 is not attached to the yoyo 104 may be referred to as off-string play. In off-string play, the string is not secured to the yoyo 104, which may be completely free of the string 106. As an example of an off-string trick that may be performed in off-string play, the string 106 may be wound about the string seat of the yoyo 104 without otherwise being secured to the yoyo 104; the yoyo 104 may then be catapulted into the air and then caught on a taut portion of the string, e.g., held between the user's hands.

FIGS. 2A and 2B include a perspective view and an exploded perspective of an example yoyo 200, arranged in accordance with at least one embodiment described herein. The yoyo 200 may include or correspond to the yoyo 104 of FIG. 1. As illustrated in FIGS. 2A and 2B, the yoyo 200 includes an axle 202, first and second bodies 204 and 206, and a string 208 (FIG. 2A). The first and second bodies 204 and 206 and the string 208 may include or correspond to the first and second bodies 108 and 110 and the string 106 of FIG. 1.

The first body 204 and the second body 206 are both coupled to the axle 202 that defines an axis of rotation 210 of the yoyo 200. In the illustrated embodiment, the axle 202 includes a double-ended bolt, e.g., a bolt with two opposing threaded ends. The first and second bodies 204 and 206 may be coupled to the axle 202 by inserting the axle 202 through holes defined in each of the first and second bodies 204 and 206 and attaching nuts 212 to the two opposing threaded ends of the axle 202 to prevent the first and second bodies 204 and 206 from being removed from the axle 202.

In other embodiments, the axle 202 may include a bolt that is inserted through the holes defined in the first and second bodies 204 and 206 where one nut is attached to one threaded end of the bolt to couple the first and second bodies 204 and 206 to the axle 202. In other embodiments, the axle 202 may have other configurations. In still other embodiments, the axle 202 may be omitted altogether, in which case the first and second bodies 204 may be coupled directly to each other.

The string 208 may be wound around a string seat of the yoyo 200, described in more detail below with respect to FIGS. 4A-4D. With the string 208 wound around the string seat of the yoyo 200, the yoyo 200 may be played by throwing the yoyo 200, with the string 208 unwinding and causing the yoyo 200 to rotate.

The axle 202 and the first and second bodies 204 and 206, as well as all other components of the yoyo 200 excluding the string 208, may have an aggregate mass, referred to as the aggregate mass of the yoyo 200. The first and second bodies 204 and 206 each have a diameter that is the same in some embodiments. A ratio of the aggregate mass of the yoyo 204 and 206 to the diameter of the first and second bodies 204 and 206 may be less than a threshold ratio. The threshold ratio may be 0.6 (grams per millimeter) in some embodiments. The threshold ratio of aggregate mass to diameter may be relatively lower than in other yoyos to ensure the thrust provided by propeller blades of the first body 204 and/or the second body 206 is sufficient to counteract or at least partially counteract effects of gravity on the yoyo 200.

Alternatively or additionally, the diameter of each of the first and second bodies 204 and 206 may be relatively larger than the diameter of some other yoyos. For example, the diameter of each of the first and second bodies 204 and 206 may be at least fourteen centimeters in some embodiments. In these and other embodiments, the yoyo 200 may be thrown in the same or a similar manner as flying discs, examples of which are commonly marketed under the mark FRISBEE.

The first body 204 includes a first outer rim 214 and first propeller blades 216, only some of which are labeled for simplicity. The first propeller blades 216 extend inward from the first outer rim 214, e.g., toward the axle 202 in FIG. 2A. More generally, the first propeller blades 216 may extend inward from the first outer rim 214 towards a center of the first outer rim 214. The first body 204 additionally includes a first drum 218 or hub. The first propeller blades 216 may extend between the first outer rim 214 and the first drum 218.

The second body 204 includes a second outer rim 220 and second propeller blades 222, only some of which are labeled for simplicity. The second propeller blades 222 extend inward from the second outer rim 220, e.g., toward the axle 202 in FIG. 2A. More generally, the second propeller blades 222 may extend inward from the second outer rim 220 towards a center of the second outer rim 220. The second body 204 additionally includes a second drum 224 or hub. The second propeller blades 222 may extend between the second outer rim 220 and the second drum 224.

In some embodiments, the first and second drums 218 and 224 may be collectively referred to as a drum of the yoyo 200. The drum of the yoyo 200, including the first and second drums 218 and 224, may surround the axle 202 at least within a gap between the first and second bodies 204 and 206 and may have a diameter greater than a diameter of the axle 202. Alternatively or additionally, a diameter of the drum may be at least 25% of the diameter of the first and second bodies 204 and 206.

In FIGS. 2A and 2B, each of the first and second bodies 204 and 206 is illustrated as including multiple propeller blades 216 or 222. In other embodiments, only one, but not both, of the first and second bodies 204 and 206 includes multiple propeller blades 216 or 222. Alternatively or additionally, each of the first and second bodies 204 and 206 may have more or fewer propeller blades 216 or 222 than are illustrated in FIGS. 2A and 2B.

Each of the propeller blades 216 and 222 has a radially variable pitch or steepness. In particular, the pitch of each of the propeller blades 216 and 222 is relatively steep at the first or second drum 218 or 224 and decreases to the first or second outer rim 214 or 220 to a pitch at the first or second outer rim 214 or 220 that is less than the pitch at the first or second drum 218 or 224. In addition, each of the propeller blades 216 and 222 has the same general variable pitch. In other embodiments, the pitch of each of the propeller blades 216 and 222 may radially increase from the first or second drum 218 or 224 to the first or second outer rim 214 or 220. Alternatively or additionally, each of the propeller blades 216 or 222 may have a constant pitch from the first or second drum 218 or 224 to the first or second outer rim 214 or 220. Alternatively or additionally, each of the propeller blades 216 or 222 within a given one of the first or second bodies 204 or 206 may have different variable or constant pitches. Alternatively or additionally, the propeller blades 216 of the first body 204 may have a different pitch than the propeller blades 222 of the second body 206.

Each of the propeller blades 216 and 222 has a pitch direction that may be clockwise or counterclockwise. Clockwise and counterclockwise pitch directions are considered herein to be opposite pitch directions. As used herein, pitch direction may refer to a direction of rotation of the first or second body 204 or 206 when oriented so the axis of rotation 210 is generally vertical that results in a generally upward thrust. In the example of FIGS. 2A and 2B, the propeller blades 216 and 222 may have a counterclockwise pitch direction. In particular, when the first and second bodies 204 and 206 are oriented with the axis of rotation 210 generally vertical, rotation of the first and second bodies 204 and 206 counterclockwise about the axis of rotation 210 may result in a generally upward thrust.

In FIGS. 2A and 2B, the propeller blades 216 of the first body 204 and the propeller blades 222 of the second body 206 have the same counterclockwise pitch direction. In other embodiments, the propeller blades 216 of the first body 204 may have an opposite pitch direction from the propeller blades 222 of the second body 206.

In addition, in FIGS. 2A and 2B, each of the first and second outer rims 214 and 220 may have a cylindrical shape. In other embodiments, one or both of the first or second outer rims 214 or 220 may have a frustoconical shape or other suitable shape.

Each of the first and second bodies 204 and 206 may be injection molded or formed in any other suitable manner from the same material, such as ABS plastic, aluminum, or other suitable material or materials. In other embodiments, each of the first and second bodies 204 and 206 may have a core made from one material, e.g., hard plastic, and an outer layer made from a softer material, e.g., rubber.

Alternatively or additionally, the yoyo 200 may include removable mass to adjust a mass of the yoyo 200. For example, the yoyo 200 may include silicone rubber bands or other removable components that may be attached to or removed from one or both of the first or second bodies 204 or 206 to adjust the mass of the yoyo 200.

Alternatively or additionally, the yoyo 200 may include one or more light emitter elements. The light emitter elements may be integrated or snapped into or otherwise attached to or included in one or both of the first or second outer rims 214 or 220 or one or both of the first or second drums 218 or 224. Each of the light emitter elements may include a battery-operated light emitting diode (LED), a piezoelectrically-operated LED, glow-in-the dark paint or decals or other glow-in-the dark element, or other suitable light emitter element.

FIG. 3 includes a perspective view of another example yoyo 300, arranged in accordance with at least one embodiment described herein. The yoyo 300 may include or correspond to the yoyo 104 of FIG. 1. As illustrated in FIG. 3, the yoyo 300 includes an axle 302, first and second bodies 304 and 306, a string 308, and nuts 312 (only one of which is visible in FIG. 3). The axle 302 may define an axis of rotation 310 of the yoyo 300. The first and second bodies 304 and 306 and the string 308 may include or correspond to the first and second bodies 108 and 110 and the string 106 of FIG. 1. The first body 304 includes a first outer rim 314, first propeller blades 316 (only some of which are labeled for simplicity), and a first drum 318. The second body 306 includes a second outer rim 320, second propeller blades 322 (only some of which are labeled for simplicity), and a second drum 324. Except as otherwise noted, the axle 302, the first and second bodies 304 and 306, the string 308, the axis of rotation 310, the nuts 312, the first outer rim 314, the first propeller blades 316, the first drum 318, the second outer rim 320, the second propeller blades 322, and the second drum 324 of FIG. 3 may have the same or similar form and/or function as the axle 202, the first and second bodies 204 and 206, the string 208, the axis of rotation 210, the nuts 212, the first outer rim 214, the first propeller blades 216, the first drum 218, the second outer rim 220, the second propeller blades 222, and the second drum 224 of FIGS. 2A and 2B and the description of the foregoing components of FIGS. 2A and 2B may similarly apply to the description of the foregoing components of FIG. 3.

In comparison to FIGS. 2A and 2B, in FIG. 3, the propeller blades 316 and 322 may have a clockwise pitch direction instead of the counterclockwise pitch direction of the propeller blades 216 and 222 of the FIGS. 2A and 2B.

FIGS. 4A-4D include side views of more example yoyos 400A-400D (collectively “yoyos 400”), each arranged in accordance with at least one embodiment described herein. Each of the yoyos 400 may include or correspond to the yoyo 104 of FIG. 1, the yoyo 200 of FIGS. 2A and 2B, or the yoyo 300 of FIG. 3.

Each of the yoyos 400 includes a first body 402A-402D (collectively “first bodies 402”), a second body 404A-404D (collectively “second bodies 404”), an axis of rotation 406A-406D (collectively “axes of rotation 406”), and a string seat 408A-408D (collectively “string seats 408”). Regarding the first bodies 402, the second bodies 404, and the axes of rotation 406, they may generally be similar in form and/or function to the first bodies 108, 204, 304, the second bodies 110, 206, 306, and the axes of rotation 112, 210, 310 described above, unless otherwise noted.

Each of the string seats 408 axially separates a respective one of the first bodies 402 from a respective one of the second bodies 404. A string, such as the strings 106, 208, 308, may be windable and unwindable about each of the string seats 408 to cause rotation of each of the yoyos 400 about the respective one of the axes of rotation 406.

The first and second bodies 402 and 404 may be separated by gaps 409A-409D (collectively “gaps 409”). The gaps 409 may be as narrow as a diameter of the string up to any desired width. Alternatively, the gaps 409 may be tapered, e.g., the gaps 409 may be relatively narrower at or near the string seats 408 and may taper out to be relatively wider at or near first outer rims of the first bodies 402 and/or second outer rims of the second bodies 404.

Each of the yoyos 400A-400C of FIGS. 4A-4C additionally includes an axle 410A-410C (collectively “axles 410”). The axles 410 may generally be similar in form and/or function to the axles 202, 302 described above, unless otherwise noted. In FIGS. 4A and 4C, the string seat 408A or 408C includes a portion of the axle 410A or 410C positioned within the gap 409A or 409C.

Each of the first bodies 402B, 402D of FIGS. 4B and 4D respectively includes a first drum 412B, 412D (collectively “first drums 412”). Each of the second bodies 404B, 404D of FIGS. 4B and 4D respectively includes a second drum 414B, 414D (collectively “second drums 414”). The first drums 412 and the second drums 414 may generally be similar in form and/or function to the first drums 218, 318 and the second drums 224, 324 described above, unless otherwise noted.

The first drums 412 and the second drums 414 each include a portion that extends axially into the gap 409B or 409D. In FIGS. 4B and 4D, the string seat 408B or 408D includes the portion of the respective one of the first drums 412 and the portion of the respective one of the second drums 414 that extends into the gap 409B or 409D. In these and other embodiments, a diameter of the string seat 408B or 408D may be at least 25% of a diameter of the first and second bodies 402 and 404.

In other embodiments, only one of the first or second drums 412 or 414 may include a portion that extends across the entire gap 409B or 409D such that the string seat 408B or 408D includes only the portion of a respective one of the first or second drums 412 or 414. Alternatively or additionally, each of the first bodies 402A, 402C of FIGS. 4A and 4C may additionally include a first drum and each of the second bodies 404A, 404C of FIGS. 4A and 4C may additionally include a second drum but without portions that extend axially within the gap 408A or 408C.

As illustrated in FIGS. 4A and 4B, a first outer rim (not separately labeled) of the first body 402A or 402B and a second outer rim (not separately labeled) of the second body 404A or 404B each includes a cylindrical shape. As illustrated in FIG. 4C, a first outer rim (not separately labeled) of the first body 402C and a second outer rim (not separately labeled) of the second body 404C each includes a frustoconical shape, the first and second bodies 402C and 404C being arranged in what is sometimes referred to as a butterfly configuration where a diameter of each of the first and second bodies 402C and 404C linearly increases beginning at the gap 409C with increasing axial distance from the gap 409C. FIG. 4D illustrates another butterfly configuration in which a diameter of each of the first and second bodies 402D and 404D non-linearly increases beginning at the gap 409D with increasing axial distance from the gap 409D.

FIG. 4D additionally illustrates an embodiment in which a discrete axle that is separate from the first and second bodies 402D and 404D is omitted. In the absence of a discrete axle, the first and second bodies 402D and 404D may be coupled directly to each other.

Although not illustrated, one or more of the yoyos 104, 200, 300, 400 described herein may include a bearing. For example, the bearing may include a ring bearing that surrounds at least a portion of a corresponding one of the axles 202, 302, 410. In these and other embodiments, a string of the yoyo may be windable around and unwindable from the bearing.

The yoyos 200, 300, 400 illustrated in FIGS. 2A-4D all include first and second bodies with outer rims and propeller blades. In other embodiments, the outer rims may be omitted, in which case the propeller blades may be more exposed than in FIGS. 2A-4D. To reduce a risk of injury to the user in these and other embodiments, the propeller blades may be made of a relatively soft or compliant material, such as rubber. Alternatively or additionally, the gap between first and second bodies in these and other embodiments may be relatively large to reduce a likelihood of a string getting tangled in the propeller blades during play.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

What is claimed is:
 1. A yoyo, comprising: an axle; a first body and a second body coupled to the axle; and a string windable about the axle within a gap between the first body and the second body; wherein the first body comprises: an outer rim; and multiple propeller blades that extend inward from the outer rim toward the axle.
 2. The yoyo of claim 1, wherein the multiple propeller blades impart a thrust on the yoyo in a direction parallel to an axis of rotation defined by the axle when the first and second bodies rotate about an axis defined by the axle.
 3. The yoyo of claim 1, wherein the second body comprises: a second outer rim; and multiple second propeller blades that extend inward from the second outer rim toward the axle.
 4. The yoyo of claim 3, wherein a pitch direction of the multiple second propeller blades of the second body is the same as a pitch direction of the multiple propeller blades of the first body.
 5. The yoyo of claim 3, wherein a pitch direction of the multiple second propeller blades of the second body is opposite from a pitch direction of the multiple propeller blades of the first body.
 6. The yoyo of claim 1, wherein the axle and the first and second bodies have an aggregate mass, each of the first and second bodies has a diameter, and a ratio of the aggregate mass in grams to the diameter in millimeters is less than 0.6.
 7. The yoyo of claim 1, further comprising a string seat that surrounds the axle within the gap with a diameter greater than a diameter of the axle and about which the string is windable, wherein: the string seat comprises: a first drum included in the first body and at which inward ends of the multiple propeller blades of the first body terminate; and a second drum included in the second body and at which inward ends of multiple second propeller blades of the second body terminate; the first drum includes a portion that extends axially from the first body to the second drum; and the second drum includes a portion that extends axially from the second body to the first drum.
 8. The yoyo of claim 7, wherein a diameter of the drum is at least 25% of a diameter of the first and second bodies.
 9. The yoyo of claim 1, wherein a length of the string is at least four feet.
 10. The yoyo of claim 9, wherein a length of the string is at least ten feet.
 11. The yoyo of claim 1, wherein a diameter of the outer rim is at least fourteen centimeters.
 12. The yoyo of claim 1, wherein at least one of the first or second bodies comprises a core of a first relatively hard material with a coating of a second material that is softer than the first relatively hard material.
 13. The yoyo of claim 1, further comprising a removable mass removable from and couplable to at least one of the first or second bodies to adjust a mass of the yoyo.
 14. The yoyo of claim 1, wherein at least one of the first or second bodies includes a light emitter element.
 15. A yoyo, comprising: a first body rotatable about an axis of rotation and that includes: a first outer rim; and multiple first propeller blades that extend radially inward from the first outer rim; a second body coupled to the first body, rotatable about the axis of rotation, and that includes: a second outer rim; and multiple second propeller blades that extend radially inward from the second outer rim; and a string seat that axially separates the first body from the second body and about which a string is windable and unwindable to cause rotation of the yoyo about the axis of rotation.
 16. The yoyo of claim 15, wherein: a ratio of an aggregate mass in grams of the yoyo to a diameter in millimeters of the first and second rims of the first and second bodies is less than 0.6; and a diameter of the string seat is at least 25% of a diameter of the first and second rims of the first and second bodies.
 17. The yoyo of claim 15, further comprising an axle that defines the axis of rotation and to which each of the first and second bodies is coupled, wherein the string seat comprises a portion of the axle positioned within a gap between the first and second bodies.
 18. The yoyo of claim 15, wherein: the first body further includes a first drum at which inward ends of the multiple first propeller blades of the first body terminate; the second body further includes a second drum at which inward ends of the multiple second propeller blades of the second body terminate; the first drum includes a portion that extends axially from the first body to the second drum; the second drum includes a portion that extends axially from the second body to the first drum; and the string seat comprises a portion of the first drum and a portion of the second drum positioned within a gap between the first and second bodies.
 19. The yoyo of claim 15, wherein: at least one of the first or second bodies comprises a core of a first relatively hard material with a coating of a second material that is softer than the first relatively hard material; the yoyo further includes a removable mass removable from and couplable to at least one of the first or second bodies to adjust a mass of the yoyo; at least one of the first or second bodies includes a light emitter element; and a length of the string is at least ten feet.
 20. A yoyo, comprising: a first body rotatable about an axis of rotation and that includes: a first hub; and multiple first propeller blades that extend radially outward from the first hub; a second body coupled to the first body, rotatable about the axis of rotation, and that includes: a second hub; and multiple second propeller blades that extend radially outward from the second hub; and a string seat that axially separates the first body from the second body and about which a string is windable and unwindable to cause rotation of the yoyo about the axis of rotation. 